Effect of the Gpc-B1 Region from Triticum turgidum ssp. Dicoccoides on Grain and Protein Yield.

Wild emmer (Triticum turgidum ssp. dicoccoides, DIC hereafter) has a functional copy of the Gpc-B1 gene, whereas commercial wheat cultivars have a deletion or a non-functional copy. The DIC allele accelerates senescence and increases grain protein content relative to the non-functional allele. Here we describe the effect of the introgression of the DIC chromosome 6BS segment including Gpc-B1 on grain and protein yield (grain yield x grain protein content) in hexaploid and tetraploid wheat. We introgressed the DIC segment into six hexaploid and three durum cultivars by six backcross generations and developed near isogenic lines (NIL) with and without the DIC segment (GPC and control lines, respectively). In 2006 and 2007, nine pairs of NILs were grown in three locations in a split-plot design with five replications. The lines were maintained disease-free by applying fungicides when necessary, to avoid the confounding effect of the linked Yr36 resistance gene. Across the six environments (year by location), the presence of the DIC Gpc-B1 allele significantly (P<0.001) increased grain protein content and protein yield, whereas its effect on grain yield was not significant (P>0.05). In common wheat, the GPC NILs showed an average increase of 7 g/kg in grain protein content and 56 kg/ha in protein yield, whereas the grain yield was decreased by less than 1% relative to the control NILs. In durum wheat, the GPC NILs showed an average increase of 13 g/kg in grain protein content and 60 kg/ha in protein yield, whereas the grain yield was decreased by 450 kg/ha relative to the control NILs. A significant interaction between Gpc-B1 and genotype was observed for grain and protein yield. Separate analyses for tetraploid and hexaploid cultivars showed the same result. Introgression of the DIC Gpc-B1 can constitute a useful resource to increase total protein in cultivated wheat.